A water molecule consists of two hydrogen atoms and one oxygen atom
Runoff flowing into a stormwater drain
The three common states of matter
Surface runoff from a hillside after soil is saturated
Phase diagram of water (simplified)
Precipitation washing contaminates into local streams
Tetrahedral structure of water
Urban surface water runoff
Model of hydrogen bonds (1) between molecules of water
Willow hedge strengthened with fascines for the limitation of runoff, north of France.
Water cycle
Soil erosion by water on intensively-tilled farmland.
Overview of photosynthesis (green) and respiration (red)
Farmland runoff
Water fountain
Runoff holding ponds (Uplands neighborhood of North Bend, Washington)
An environmental science program – a student from Iowa State University sampling water
Total water withdrawals for agricultural, industrial and municipal purposes per capita, measured in cubic metres (m³) per year in 2010
A young girl drinking bottled water
Water availability: the fraction of the population using improved water sources by country
Roadside fresh water outlet from glacier, Nubra
Hazard symbol for non-potable water
Water is used for fighting wildfires.
San Andrés island, Colombia
Water can be used to cook foods such as noodles
Sterile water for injection
Band 5 ALMA receiver is an instrument specifically designed to detect water in the universe.
South polar ice cap of Mars during Martian south summer 2000
An estimate of the proportion of people in developing countries with access to potable water 1970–2000
People come to Inda Abba Hadera spring (Inda Sillasie, Ethiopia) to wash in holy water
Icosahedron as a part of Spinoza monument in Amsterdam.
Water requirement per tonne of food product
Irrigation of field crops
Specific heat capacity of water

Surface runoff (also known as overland flow) is the flow of water occurring on the ground surface when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil.

- Surface runoff

Water moves continually through the water cycle of evaporation, transpiration (evapotranspiration), condensation, precipitation, and runoff, usually reaching the sea.

- Water
A water molecule consists of two hydrogen atoms and one oxygen atom

6 related topics

Alpha

Tap water is drinking water supplied through indoor plumbing for home use in many countries.

Drinking water

Tap water is drinking water supplied through indoor plumbing for home use in many countries.
Drinking water vending machines in Thailand. One litre of potable water is sold (into the customer's own bottle) for 1 baht.
Diagram of water well types
EPA drinking water security poster from 2003
Water treatment plant
Solar water disinfection application in Indonesia
World map for SDG 6 Indicator 6.1.1 in 2015: "Proportion of population using safely managed drinking water services"
% of the population with access to drinking water
Population in survey regions living without safely managed drinking water as reported by the WHO/UNICEF JMP.
Project in Nepal: unboxing the water filter unit.
Illustration of a typical tap water treatment process

Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water.

Inorganic minerals generally enter surface water and ground water via storm water runoff or through the Earth's crust.

Water cycle

Time-mean precipitation and evaporation as a function of latitude as simulated by an aqua-planet version of an atmospheric GCM (GFDL's AM2.1) with a homogeneous “slab-ocean” lower boundary (saturated surface with small heat capacity), forced by annual mean insolation.
Global map of annual mean evaporation minus precipitation by latitude-longitude
Relationship between impervious surfaces and surface runoff
Diagram of the water cycle
Natural water cycle

The water cycle, also known as the hydrologic cycle or the hydrological cycle, is a biogeochemical cycle that describes the continuous movement of water on, above and below the surface of the Earth.

The water moves from one reservoir to another, such as from river to ocean, or from the ocean to the atmosphere, by the physical processes of evaporation, condensation, precipitation, infiltration, surface runoff, and subsurface flow.

An illustration showing groundwater in aquifers (in blue) (1, 5 and 6) below the water table (4), and three different wells (7, 8 and 9) dug to reach it.

Groundwater

An illustration showing groundwater in aquifers (in blue) (1, 5 and 6) below the water table (4), and three different wells (7, 8 and 9) dug to reach it.
Dzherelo, a common source of drinking water in a Ukrainian village
The entire surface water flow of the Alapaha River near Jennings, Florida, going into a sinkhole leading to the Floridan Aquifer groundwater
Groundwater may be extracted through a water well
Diagram of a water balance of the aquifer
Iron (III) oxide staining (after water capillary rise in a wall) caused by oxidation of dissolved iron (II) and its subsequent precipitation, from an unconfined aquifer in karst topography. Perth, Western Australia.
Groundwater withdrawal rates from the Ogallala Aquifer in the Central United States
Center-pivot irrigated fields in Kansas covering hundreds of square miles watered by the Ogallala Aquifer

Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations.

These changes can have other effects on the land above the groundwater: as an example a 2020 study published in Nature found that coastal groundwater in California would rise in many aquifers, increasing risks of flooding and runoff challenges.

An inland lake, an example of surface water

Surface water

An inland lake, an example of surface water
The entire surface water flow of the Alapaha River near Jennings, Florida going into a sinkhole leading to the Floridan Aquifer groundwater.
A stream gauge used to measure surface water.

Surface water is water located on top of the Earth's surface, and may also be referred to as blue water.

In common usage, it is usually used specifically for terrestrial (inland) waterbodies, the vast majority of which is produced by precipitation and runoff from nearby higher areas.

Water cycle of the Earth's surface, showing the individual components of transpiration and evaporation that make up evapotranspiration. Other closely related processes shown are runoff and groundwater recharge.

Evapotranspiration

Term used to refer to the combined processes by which water moves from the earth’s surface into the atmosphere.

Term used to refer to the combined processes by which water moves from the earth’s surface into the atmosphere.

Water cycle of the Earth's surface, showing the individual components of transpiration and evaporation that make up evapotranspiration. Other closely related processes shown are runoff and groundwater recharge.
Monthly estimated potential evapotranspiration and measured pan evaporation for two locations in Hawaii, Hilo and Pahala.
Classification of RS-based ET models based on sensible heat flux estimation approaches

It will usually be less because some water will be lost due to percolation or surface runoff.

Potential evapotranspiration (PET) is the amount of water that would be evaporated and transpired by a specific crop, soil or ecosystem if there were sufficient water available.

A rosette sampler is used for collecting water samples in deep water, such as the Great Lakes or oceans, for water quality testing.

Water quality

A rosette sampler is used for collecting water samples in deep water, such as the Great Lakes or oceans, for water quality testing.
Regional and national contamination of drinking water by chemical type and population size at risk of exposure
An automated sampling station installed along the East Branch Milwaukee River, New Fane, Wisconsin. The cover of the 24-bottle autosampler (center) is partially raised, showing the sample bottles inside. The autosampler collects samples at time intervals, or proportionate to flow over a specified period. The data logger (white cabinet) records temperature, specific conductance, and dissolved oxygen levels.
Filtering a manually collected water sample (grab sample) for analysis
Testing water in the Gulf of Mexico after the Deepwater Horizon oil spill
A gas chromatograph- mass spectrometer measures pesticides and other organic pollutants
Atomic fluorescence spectroscopy is used to measure mercury and other heavy metals
An electrical conductivity meter is used to measure total dissolved solids

Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage.

Industrial and commercial activities (e.g. manufacturing, mining, construction, transport) are a major cause of water pollution as are runoff from agricultural areas, urban runoff and discharge of treated and untreated sewage.